Download Version 6.4 User Manual © Copyright Inivis Limited 2008

Version 6.4
User Manual
© Copyright Inivis Limited 2008
Introduction .........................................................................................................................5
Welcome to AC3D...........................................................................................................................................5
AC3D terminology ..........................................................................................................................................5
Vertex ..........................................................................................................................................................5
Surface ........................................................................................................................................................5
Surface normal .............................................................................................................................................5
Object ..........................................................................................................................................................5
Group...........................................................................................................................................................5
Select-mode .................................................................................................................................................6
Material ........................................................................................................................................................6
Texture.........................................................................................................................................................6
Texture coordinates ......................................................................................................................................6
Bounding box ...............................................................................................................................................6
Getting help....................................................................................................................................................6
Windows/Views....................................................................................................................7
Control panel..................................................................................................................................................7
Toolbar ...........................................................................................................................................................7
View windows.................................................................................................................................................7
Orthographic (2D) views.................................................................................................................................9
Navigating in 2D views ..................................................................................................................................9
The grids ......................................................................................................................................................9
Using Background Images.............................................................................................................................9
3D views ....................................................................................................................................................... 10
Navigating in 3D ......................................................................................................................................... 10
Taking a snapshot image ............................................................................................................................. 11
Inspect mode................................................................................................................................................ 11
Creating AC3D objects ......................................................................................................12
AC3D Surfaces ............................................................................................................................................. 12
Crease angles ............................................................................................................................................ 12
One-sided and Two-sided surfaces .............................................................................................................. 13
Surface normals.......................................................................................................................................... 13
Creating new objects.................................................................................................................................... 13
Polys/Polylines/Lines................................................................................................................................... 14
Spheres, boxes etc. .................................................................................................................................... 14
Naming objects ........................................................................................................................................... 14
Lights ......................................................................................................................................................... 15
Object mode lock ......................................................................................................................................... 15
Creating other objects .................................................................................................................................. 15
Selecting, resizing, moving and rotating..........................................................................16
Selecting ...................................................................................................................................................... 16
Resizing........................................................................................................................................................ 16
Moving.......................................................................................................................................................... 17
Rotating........................................................................................................................................................ 17
Extending/Negating the selection................................................................................................................. 17
Clearing the selection................................................................................................................................... 18
Hiding objects .............................................................................................................................................. 18
Locking objects ............................................................................................................................................ 18
Model manipulation ...........................................................................................................19
Operations on objects .................................................................................................................................. 19
Texture....................................................................................................................................................... 19
Revolve ...................................................................................................................................................... 19
Mirror ......................................................................................................................................................... 20
Boolean...................................................................................................................................................... 21
Optimize Vertices........................................................................................................................................ 21
Optimize Surfaces....................................................................................................................................... 21
Reduce ...................................................................................................................................................... 21
Subdivide + / Subdivide - ............................................................................................................................. 22
Commit subdivision ..................................................................................................................................... 23
Re-centre ................................................................................................................................................... 23
Minimum-centre .......................................................................................................................................... 23
Fragment.................................................................................................................................................... 23
Merge ........................................................................................................................................................ 24
Explode ...................................................................................................................................................... 24
Extrude Along Path ..................................................................................................................................... 24
Operations on surfaces ................................................................................................................................ 25
Extruding.................................................................................................................................................... 25
Flip normal ................................................................................................................................................. 28
Change vertex order ................................................................................................................................... 28
Flip Triangle Edge ....................................................................................................................................... 29
Divide......................................................................................................................................................... 29
Combine..................................................................................................................................................... 29
Flatten........................................................................................................................................................ 30
2
Spike.......................................................................................................................................................... 30
Indent......................................................................................................................................................... 30
Bevel.......................................................................................................................................................... 30
Make hole .................................................................................................................................................. 31
Triangulate ................................................................................................................................................. 31
Spline......................................................................................................................................................... 31
Cut away object .......................................................................................................................................... 31
Remove surface only................................................................................................................................... 32
Calculate surface area................................................................................................................................. 32
Operations on Vertices................................................................................................................................. 32
Snap Together ............................................................................................................................................ 32
Snap Together by Distance ......................................................................................................................... 32
Snap to Grid ............................................................................................................................................... 32
Snap Objects by Vertices ............................................................................................................................ 32
Smooth Shape ............................................................................................................................................ 32
Align to Axis................................................................................................................................................ 32
Weld .......................................................................................................................................................... 33
Unweld....................................................................................................................................................... 33
Insert Vertex ............................................................................................................................................... 33
Divide Triangle Edge ................................................................................................................................... 33
Extrude Edges ............................................................................................................................................ 33
Slice Surface .............................................................................................................................................. 33
Create Convex Surface/Object..................................................................................................................... 34
Create Ordered Surface .............................................................................................................................. 35
Create Quad............................................................................................................................................... 35
Create 2D Mesh.......................................................................................................................................... 36
Boolean operations ...................................................................................................................................... 37
Subtract ..................................................................................................................................................... 37
Intersect ..................................................................................................................................................... 37
Union ......................................................................................................................................................... 38
Cut away .................................................................................................................................................... 38
Knife .......................................................................................................................................................... 39
Knife and Cut Away..................................................................................................................................... 39
Boolean examples ........................................................................................................................................ 40
Cutting a round-ended channel in a cylindrical object .................................................................................... 40
Cutting an aileron from a wing...................................................................................................................... 40
Cutting multiple windows from a fuselage ..................................................................................................... 41
Cutting a solid object at an angle ................................................................................................................. 41
Hints and Tips .............................................................................................................................................. 43
Subdivision Surfaces ........................................................................................................44
Changing the subdivision level .................................................................................................................... 44
Switching display of subdivisions................................................................................................................ 44
Committing subdivisions ............................................................................................................................. 45
Examples...................................................................................................................................................... 45
Hints and tips ............................................................................................................................................... 46
Using Extrude to add detail .......................................................................................................................... 46
Display or hide subdivisions? ....................................................................................................................... 47
Choosing the right subdivision level.............................................................................................................. 47
Advanced users .......................................................................................................................................... 47
Texturing............................................................................................................................48
Setting a texture ........................................................................................................................................... 48
Changing the mapping ................................................................................................................................. 48
Changing the texture repeat and offsets ...................................................................................................... 48
Tools ..................................................................................................................................50
Model Information ........................................................................................................................................ 50
Render.......................................................................................................................................................... 50
Object Hierarchy........................................................................................................................................... 50
Object Property Editor.................................................................................................................................. 51
Texture Coordinate Editor ............................................................................................................................ 52
Selecting and manipulating .......................................................................................................................... 53
Remapping the selection ............................................................................................................................. 54
Replicator ..................................................................................................................................................... 54
Create Text ................................................................................................................................................... 56
Align Objects................................................................................................................................................ 56
Position 3D cursor........................................................................................................................................ 56
Materials ............................................................................................................................57
The palette.................................................................................................................................................... 57
Editing Palette entries .................................................................................................................................. 57
Loading and saving files ...................................................................................................58
Importing other formats ............................................................................................................................... 58
Triangle files ............................................................................................................................................... 58
Vector files ................................................................................................................................................. 58
Exporting files .............................................................................................................................................. 58
3
3D Studio (3ds)........................................................................................................................................... 58
VRML 1...................................................................................................................................................... 58
VRML 2...................................................................................................................................................... 58
VRML2 Proto.............................................................................................................................................. 58
DIVE .......................................................................................................................................................... 59
MASSIVE ................................................................................................................................................... 59
RENDERMAN ............................................................................................................................................ 59
POV-Ray.................................................................................................................................................... 59
Triangle files ............................................................................................................................................... 59
Object Library............................................................................................................................................... 59
Rendering ..........................................................................................................................60
A POV-Ray example ..................................................................................................................................... 60
Appendix............................................................................................................................62
3D Mouse support ........................................................................................................................................ 62
Plugins ......................................................................................................................................................... 63
Performance tips .......................................................................................................................................... 63
Key-presses ................................................................................................................................................. 63
Preferences/settings .................................................................................................................................... 64
Additional Information.......................................................................................................65
Third-party plugins ....................................................................................................................................... 65
Greeble ...................................................................................................................................................... 65
4
Introduction
Welcome to AC3D
AC3D is designed to make the construction of 3D objects fast and easy. It is used to create 3D models for
simulations, games, rendering ray-traced images and for scientific and general data visualization.
AC3D runs on a wide range of standard hardware and is available across a number of popular platforms.
AC3D terminology
Vertex
A vertex is a single point in 3d space. It’s specified by three coordinates x, y and z. More than one vertex can
occupy the same position in 3d space. A vertex is always owned by a single object; they cannot be shared between
objects. A vertex is usually part of one or more Surfaces, but need not be.
Surface
A surface in AC3D is a sequence of vertices. Surfaces are one of three types; polygons, lines or polygon outlines.
The type of a surface defines how the surface is drawn and this can be easily changed. If a surface is set to be
single-sided, it will only be visible from the front. Two-sided surfaces will be visible from both sides. It is more
efficient to draw single sided surfaces and makes more sense when used as part of an object such as a sphere
(where you can’t see the other side of the surfaces). Surfaces have a material attribute, which defines the color and
quality (for lighting purposes). Each vertex referenced in a surface has an associated Texture Coordinate. Vertices
can be shared between surfaces in the same object.
Surface normal
A ‘surface normal’ specifies the direction a surface is facing. Normals are used in lighting calculations. Surface
normals are automatically calculated by AC3D. A surface is defined as facing the viewer if the vertices can be seen
in an anti-clockwise direction.
Object
An AC3D object is a list of vertices, and surfaces that use these vertices. It also has other attributes such as a name
and texture.
Group
A group is a special object that has no surfaces or vertices but has other objects as children. Groups are created by
selecting two or more objects and selecting ‘Group’ from the edit menu or toolbar. Use the ‘Ungroup’ function to
separate the objects.
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Select-mode
The select mode allows control over the level of editing in AC3D. In ‘Vertex’, individual vertices can be selected and
adjusted. In ‘Surface’, operations are performed on one or more selected surface. In ‘Object’, whole objects are
selectable. This allows manipulation of objects, even if they are part of groups. In ‘Group’, selecting all or part of an
object automatically selects the top level object.
Material
A material defines the color of a surface and also the attributes that define the way it will react to light e.g. shininess.
Texture
Graphical images can be mapped onto the surfaces of an object. The images are usually from graphics files such as
gif, jpg, bmp etc.
Texture coordinates
When the vertex of a surface is drawn, a texture coordinate specifies the position of a texture image to map to that
point. A texture coordinate is a two dimensional (u,v) value which defines the point on the 2D image.
Bounding box
When you make a selection of objects, surfaces or vertices, a green box outlines it. You can drag, resize or rotate
this box to adjust the contents
Getting help
User interface components in AC3D have ‘balloon help’. Small
‘tooltip’ windows will popup when the mouse pointer rests over a
button or field label.
This feature can be switched off from File->Settings.
When browsing through the menu items, the function on each
item is described in the message text at the bottom of the AC3D
window.
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Windows/Views
AC3D has a control panel on the left, plus 4 view windows. There’s also the menu and toolbar at the top and an
information bar along the bottom.
Control panel
This is where the main controls over the selection and draw modes are located. It also
contains the surface-type controls, the palette of materials and the object name field.
The top of the control panel shows information about the current selection. When the
mouse is being used to interact with models, this area will also display current positions,
distances moved and other related information.
Toolbar
This contains buttons for some of the most commonly used functions.
All
None
Dup
Cut/Copy/Paste
Group/Ungroup
Flip x/y/z
200%/50%/+10%/-10%
select everything
clear the selection
duplicate the selection
use AC3D’s internal clipboard
put selected objects into a group/remove the group object
flip the section about this axis
scale the selection uniformly
Maximize a single view or view ALL together
View windows
By default, AC3D starts with three two-dimensional (2D orthographic) view windows and a single three-dimensional
(3D) window. The default view windows show Front, Left, Top and 3D camera angles onto the model space.
7
The dividers between the 4 view windows can be dragged to resize the views. Individual views are maximized by
clicking on the view buttons at the top right of the main window (alternatively, the F1-F5 keys can be pressed to
switch between the different view configurations).
The main window size/position and other settings are saved when AC3D exits.
The configuration of the views that AC3D starts up with can
easily be changed from the menu Views->Configure views.
Each view window has an individual menu at the
top. This contains the menu for the view angle
(Camera), changing the viewpoint (e.g. focusing
on the currently selected area) and some misc.
controls that are dependent on whether the
window is set to 2D or 3D.
The Camera angle can be changed at any time. This is useful if, for example, you need to view (or work on) a model
from the underside (bottom view).
The icons on the right of each view-m enu allow you to use the mouse to navigate around the 3D space, show a clean
image, and maximize the view window.
Spin (3D views only) – press and drag
Move/Pan view- press and drag
Zoom in/out view – press and drag
Inspect – Switch to show clean image (display without all
surface outlines, grid, controls etc) and change to simple
navigation mode.
Maximize/minimize view button
The spin, move/pan and zoom button are special controls that are held down (left mouse button) whilst the mouse is
dragged. The views adjust their viewpoint as the mouse is dragged.
Additional views can be created from the menu Views->New-View.
8
Unlike 2D CAD programs, the space presented in the AC3D view windows is not like a finite piece of paper which
has a limit and edges. You can move viewpoints just like a person moves around in real 3D space. There are no
real edges to the available space (apart from reaching computational limits).
Orthographic (2D) views
When a view camera is set to Front, Back, Top, Bottom, Left or Right, the view is non-perspective orthographic 2D.
An orthographic view shows a view parallel to a single axis.
The items on the main ‘Orth’ menu control how views set to these camera modes are drawn and what components
are visible. For these settings, all Orth windows work together e.g. switching from filled to wireframe appearance in
one Orth window causes all other Orth windows to also be set to wireframe.
Although it’s useful sometimes to work in a single view, seeing all the windows at once can be very helpful when
positioning objects and laying out scenes.
Navigating in 2D views
Use the mouse to pan or zoom an orth view. The keyboard arrow keys pan and control+up/down zooms in and out.
Holding down a shift key increases the movement/zoom distance.
The grids
In the orthographic windows there are two grids - the draw grid (major lines) and the snap grid (minor lines). Both can
be set from 'File->Settings' and their display can be toggled on/off by selecting ‘Grid’ from the Orth menu (or pressing
the ‘g’ key when focused in an orth window).
The Snap grid is shown by thin visual guide lines; the draw grid uses thicker lines. If ‘Gridsnap’ is switched on,
moving/resizing/creating mouse movements will be aligned to the nearest snap grid points.
The grids can be configured to display units of any size e.g. for eighths of an inch, the major draw grid would be set
to 1.0 and the snap grid set to 0.125 (1/8th).
Using Background Images
Any orthographic (2D) window can display a background image. This can be useful for tracing shapes or laying out
objects in relation to a scanned image e.g. a plan or map. Background images are set and unset from the Orth menu
at the top of an orthographic window. All image formats that are supported by AC3D's texture loaders can be used
as background images.
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Background im ages will scale and move with the views.
By default the image will be centered on the origin. The
scale and position of the background im age is adjusted by
using alt and the cursor keys. Alt and the cursor keys
reposition the image, whilst Alt+Shift plus cursor up/down
scale the image.
Details of background images are currently not saved with
models or when AC3D exits.
3D views
A 3D view window displays the current model in a three
dimensional perspective and changes instantly when any
modifications are made to the current model.
The main 3D menu (at the top of the main AC3D window)
contains controls to switch visibility of many attributes within
the 3D window. Changing these controls affects all 3D
windows within the program.
A 3d grid is available - toggle with 'g'. The grid lies on the XZ
plane (floor).
'w' toggles between wireframe and filled drawing, 't' toggles
textures. 'l' toggles the fixed light. See the 3D menu for
more viewing options.
Navigating in 3D
Two navigation modes are available in this window – ‘spin’ and ‘walk’. These can be switched from the view’s own
3D menu or by pressing the ‘1’ or ‘2’ keys whilst the pointer is in the 3D window.
Spin mode
Button controls at top of view for spin, pan and zoom
From keyboard:
Spin- up/down/left/right keys, or Alt+left mouse button
Zoom – Control+up/down
Walk mode
Button controls at top of view for walk/fly, pan and tilt
From keyboard:
Move forward - up-key
Move backward - down-key
Turn - left/right keys
Move up/down – alt+up/down
Holding down the shift key with the above combinations
increases the distance of travel
10
Taking a snapshot image
Windows and Mac users can quickly copy the image shown in a view
to the system clipboard by selecting the item on the Camera menu,
which is on each View window.
After selection of this menu item, you may switch to another program
e.g. an im age editor or word processor program and then ‘Edit->Paste’
within that in order to insert the image
The same function is also available on the Edit menu (for the main 3D
view). Note that the ‘Copy’ item on the Edit menu is used for the
internal AC3D clipboard, the item that copies the image to the system
must be used to retrieve the image.
To increase the quality of the image, anti-aliasing can be switched on
(from the view’s 3D menu). This ‘smooths’ the image. Anti-aliasing
slows down rendering of the 3D image so it’s recommended that it
only be used when preparing images for a snapshot.
Inspect mode
Pressing down the eye icon, which is available on each view, sets the view into Inspect mode. Inspect mode
switches off the display of vertices, surface outlines etc so that a ‘clean’ image is displayed. It also changes the way
that you can navigate the view. When inspect mode is on, simply dragging the mouse navigates (normally the alt key
would be used).
Inspect mode is useful if you are performing a lot of work in the other views and using one view for previewing the
changes. It’s also useful with additional monitors, where one monitor has a single AC3D view (Views->New-View)
that is set to inspect. Work can be performed on the main monitor and inspected (quickly spin or walk) on the other
monitor.
11
Creating AC3D objects
AC3D Surfaces
Objects in AC3D consist of a collection of vertices and a number
of surfaces that reference those vertices. A surface may be one
of three types: Polygon, Polyline or Line. A polygon is a filled
area, a Polyline is a wire-frame outline of the polygon (a loop that
joins the start vertex to the end),and a Line has a specific start
and end.
Surface type is changed by pressing a button on the control panel.
The Surface type buttons are located at the bottom of the control
panel (Poly, Polyline, Line):
This panel also contains controls to set surfaces to be smooth or
flat This determines the way that a polygon is drawn (it has no
effect on Lines or Polylines).
If a surface is flat-shaded, the color across the surface will be
constant. If it is shaded then the color will be 'graded' depending on
lighting conditions.
Vertices can be shared between surfaces (i.e. one or more
surfaces use the same vertex). If these surface types are set to
‘smooth’, the effect is of one continuous 'sm ooth' surface. The
vertices MUST be shared for two surfaces to be smoothed
together. This m ethod of shading allows smooth- looking objects to
be created from relatively simple shapes.
Crease angles
Each AC3D object has a crease-angle property. This is adjusted via the Tools->Object Property Editor. The crease
angle is specified in degrees and is used to determine if adjacent surfaces in the object should be ‘smoothed
together’ by averaging the surface-normals. The angle between adjacent surfaces is measured and if this is larger
than the crease angle the surfaces will be smoothed.
A crease angle of zero degrees forces all surfaces to be flat. A crease angle of 180 degrees forces all surfaces to be
drawn smooth.
Setting a surface type to ‘flat’ forces the surfaces to remain flat shaded. Setting a surface type to smooth allows it to
be under control of the crease angle.
Example: a cylinder with all surfaces set to ’Smooth’.
crease angle = 0°
All surfaces appear flat.
crease angle = 45°
Crease angle = 91°
The
cylinder
edges
are
‘smoothed together’ but the
end is flat because the angle
between it and the edges is >
45°
The cylinder sides are now
shaded along with the edges.
12
One-sided and Two-sided surfaces
The '1S' and '2S' buttons select how many sides a surface has (one-sided or two-sided). If a surface is single sided, it
will only be visible from one side. The following pictures dem onstrate this:
In this model, there are three objects - a green rectangle,
a red rectangle and a blue ellipse (made by creating an
ellipse object and setting the surface type to be ‘Poly’).
The red rectangle has been set to be single-sided '1S'.
This means that it is visible from the 'front' but not from
the back (the second image shows the whole model
rotated).
Objects such as spheres and cubes, which do not have any interior surfaces visible, benefit from a speed
optimization when being drawn with the surfaces single-sided.
Surface normals
The direction a surface is facing is determined by its 'Normal' (indicated by arrows in the above diagram). This is a 3D
graphics term for a line at right angles to the surface that indicates a direction). Normals are used to calculate
surface colors and shading when the objects in AC3D are drawn. For smooth shading, vertex normals are
automatically calculated by averaging norm als of all connected surfaces.
Normals can be visualized in both the orthographic and 3d views (‘Normals’ on the ‘orth’ and ‘3d‘ menus). This
preview is useful for solving problems where, for example, some surfaces in an object are the wrong way around.
This can cause surfaces to appear missing if they are one-sided, or the smoothing can appear uneven. Viewing the
normals is also handy for use with the extrude function and can help determine the extrude settings that ensure that
new surfaces face in the correct direction.
This picture shows two spheres. The sphere on the
left shows correct normals (i.e. all facing outwards).
The sphere on the right shows some surfaces facing
in the wrong direction. Notice how the shading is not
consistent.
AC3D automatically calculates the normals (both
surface and vertex).
To flip the direction of a surface, use Surface->Flip Normal. (This actually reverses the order of the vertices in the
surface so that the automatically generated normal faces the opposite way).
Creating new objects
The AC3D control panel contains a number of 2D and
3D object shapes that can be created.
New objects are created by selecting one of these
buttons and clicking/dragging in one of the view
windows.
13
Polys/Polylines/Lines
To create a Poly/Polyline/Line, click to position each point and either doubleclick or press the middle or right mouse button to end. The surface type can
be altered later from the control panel if you need a different type.
These objects consist of a list of vertices and a single surface. The surfaces from more than one of these objects
can be collected together into a single object by using the Object->Merge function.
Polygons should be 3 or more points. Concave polygons are handled by AC3D. They can be converted to triangles
by using the Surface->Triangulate function.
It is possible to draw a line or poly in different windows - creating a non-planar surface. This makes sense with lines
but is not correct for a polygon which should have all of the points on the same plane. Invalid polygons i.e. polygons
that have less than three vertices are displayed in a cyan color. Surfaces that have crossing edges are displayed in a
red color.
This shows part of a sphere where
some vertices have been deleted.
Polygon surfaces with only 2 vertices
have been left. These can be
removed by using Object->Optimize
Surfaces.
This shows a four point polygon where the
vertices are positioned so that the edges
overlap. This is fixed by moving the vertices.
To draw shapes that have vertices in the sam e position as an existing shape, use the ‘Nearsnap’ function; the control
for which appears under the draw mode section when /Poly/Polyline/Line mode is selected. When Nearsnap is on,
the next point drawn will ‘snap’ to the nearest existing vertex (when there is a vertex within a certain range).
Spheres, boxes etc.
Creating a 3D object by dragging the mouse in a window specifies two of
the dimensions for the new object - the third dimension is an average of
the original two. The location of the object in the third dim ension is
specified by the 3D cursor.
These objects can also be created with a single click in a view window.
This will create a regular object that fits into a 1 x 1 x 1 square.
The 3D cursor is shown in the orthographic views by a cross. This is repositioned by using the tool, Tools->Position3D-Cursor. Most people rarely use this because it is very easy to create an object and position it afterwards.
Some object types allow parameters to be set before
creating the object. For example, spheres and meshes
can be made from triangles or quads.
Controls for any available parameters appear in the
panel underneath the Mode box on the control panel.
Naming objects
When created, AC3D Objects are automatically named. The object name box is at the bottom of the control panel
and allows these nam es to be set.
14
Object names can only be edited/set in Group or Object select mode. Object names need not be unique and can be
the same across multiple objects. This can be useful for selecting or finding particular objects with the Edit->Selectby-name function (e.g. to select all objects named ‘chair’). Object names are used in some of the file formats
exported by AC3D.
If AC3D is being used to generate VRML or Dive files, URLs and other text can be associated with objects. This text
is used in a number of the export file formats that AC3D generates. The names, text and URLs are saved in the .ac
AC3D files. Text attached to each object is entered into the field on the Tools->Object Property Editor window.
Object names can also be set in the property editor.
Lights
Lights have no associated geom etry and represent a ‘point light’. In the AC3D views, lights are represented by this
symbol:
Lights are fixed brightness white lights. Lights are selected and repositioned in Group or Object select mode.
Lights are generated in exported files such as POV and RIB files. The generated files can be edited to alter the
lighting attributes.
This image shows a green sphere with two lights (indicated by white spheres) the main headlight is off. (The headlight in the 3D window is toggled on and off
with the 'l' key, or from the main ‘3D’ menu).
If the headlight is on when POV or RIB files are generated, a light will be added to inform ation in the file.
Object mode lock
Clicking twice on an object mode button causes the m ode to
‘lock’. This is indicated by the button changing to green. When a
mode is locked, the mode does not revert to Move/size after an
object is created. Pressing Move/Size, Rotate (or extrude)
releases the lock.
Creating other objects
It is very easy to create other objects from these shapes.
ellipse and select Object->Revolve.
For example, to make a torus shape (‘donut’), create an
A cone can be made in a number of ways. Create a cylinder; select one end (in vertex mode) and select Vertex>Snap Together. A cone made this way will have the texture coordinates set correctly. For a simpler cone (fewer
vertices), optimize the vertices with Object->Optimize Vertices. This means that the centre-point of the cone will be a
single vertex which is shared with all the sides. Some other ways of making cones include making a 'disk' and pulling
the centre point up or using Object->Revolve to revolve a line around an axis.
‘Extrude’ is used to add extra parts to objects or to give 2d shapes depth. Objects can be cut into pieces and specific
surfaces deleted.
15
Selecting, resizing, moving and rotating
In AC3D, the manipulation of 3D objects works in a very similar way to a 2D drawing program i.e. the selection is
shown highlighted and ‘handles’ can be moved to reshape the section.
Selected components (surface, vertices) are shown in a
different color and are surrounded by a ‘bounding box’
(usually green).
Selection is possible in move/size, rotate and extrude modes.
The default mode is move/size.
Selecting
The Select-mode defines the granularity of selection i.e. it determines if selections will affect objects, groups or
vertices. To select in AC3D, either click the left mouse button or use the left mouse button to drag a box over an
area. When something is selected, the bounding-box that appears can be dragged or resized, directly affecting the
points/surfaces/objects.
Vertex mode
vertices can be selected by a single click on a single vertex or by dragging a box
over a number of vertices
Surface-mode
a single surface is selected by a click . Multiple surfaces are selected by dragging a
box over an area
Object-mode
selecting any part of an object causes the whole object to be selected
Group-mode
a group of objects can be selected by highlighting any part of a single object that
belongs to a group
There is an important difference between a click-select and a drag -select. Click-selects are used for selecting single
entities e.g. one object, one surface, one vertex. A click- select will select the nearest entity underneath the pointer.
A drag-select will select everything within the drawn box that lies underneath the region. Click-select is useful, for
example, when selecting a single surface of a sphere (where a drag -select will always select more than one
surface).
Selections are preserved between changes of select modes. Changing from vertex to surface select-mode means
that any surfaces that have all vertices selected will remain selected in surface-mode.
Resizing
Dragging the ‘handles’ at the corners of the bounding box, using
the left mouse-button, resizes the selection.
Holding down the control key whilst dragging an edge handle
resizes opposite edges. On the corner handles, holding down
the control key scales the selection uniformly.
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Resize selections of vertices and surfaces
It is possible to resize a selection down to zero width/height. This is useful for lining up vertices.
Moving
The green bounding box is dragged with the left mouse button to
reposition the selection.
Holding the control key down whilst dragging, constrains
movement to up/down or left/right only.
In a 3D view, AC3D displays green arrows on each side of the
bounding box. These can be dragged to move the selection.
Rotating
When the rotate button is selected, clicking on the bounding box
and dragging left/right will rotate the selection about the point of
the first click.
Extending/Negating the selection
Holding down the shift key whilst selecting with the left mouse button extends the selection (adds new entities).
Pressing shift whilst selecting with the 2nd (or 3rd) mouse button negates (subtracts) items from the current selection.
Extend and negate selection work in all select modes.
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This picture shows the top and bottom of a sphere selected. This is done by first
selecting the top vertices with a drag, then holding down the shift key and
dragging across the bottom of the sphere.
Clearing the selection
Clicking outside the area of the bounding box will cause everything to become unselected.
The selection can also be cleared by pressing the ‘None’ button in the toolbar or from the menu Edit->Select Nothing.
Hiding objects
Hiding allows objects to be temporarily removed from
the views. The current selection, or objects that are
not selected, can be hidden from view. The 'Unhide'
button ensures that all objects are visible. The ‘Show
Hidden’ toggle in the main 3D menu determines if the
hidden objects are visible in 3d views. Hiding is useful
when access is needed to work on obscured objects.
Locking objects
Locking is useful for temporarily disabling objects that
are obscuring others. When objects are locked, it’s not
possible to select them.
Locking also helps with the speed performance when
editing large models. It works in a similar way to hiding,
except that locked objects are drawn in grey wireframe.
Note that if objects are hidden (or locked) and the model is saved/exported, hidden and locked objects are included
in the file.
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Model manipulation
Operations on objects
These operations are on the ‘Object’ menu and act upon one or more selected objects.
Texture
Each object can have one texture. A texture is a 2D bitmap image, such as a .gif or .jpg file, which is drawn onto the
surfaces of an object.
To set a texture on an object, use Object->texture->Load texture. AC3D’s default palette of objects predefine the
way that the textures are mapped onto the object surface. To adjust this, or to define a custom mapping, use AC3D’s
Texture Coordinate Editor (Tools menu). See the section on ‘Texturing’.
Revolve
Revolving makes copies of the selected objects, rotating each copy, and then creating surfaces between the copies.
It’s recommended that this function be used to revolve 2D outlines of shapes rather than filled-polygon objects. Any
revolved line objects are automatically removed after the revolution. The axis around which the revolution is
performed can be altered.
To create a torus - make a circle in the Front window:
Select 'Object->Revolve…'
Set the axis to Y and click Revolve. You should see
something like this:
Select the 'smooth' surface type (near the bottom
of the control panel) to make it appear rounded
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The degrees of revolution can also be
altered- e.g. 270 degrees:
If there are points that need to be in the centre of the final revolved object - (e.g. the start and end points of the cup
profile above) then these points should lie exactly on the axis. Drawing the line with ‘Gridsnap’ can ensure this.
Alternatively, snapping the points to the grid (Vertex->Snap to Grid) or by using the control panel Move-to function to
ensure that two of the values are zero. If these points are not exactly on the axis a small hole or possibly overlapping
surfaces will be created. If this happens, the 'Vertex->Snap Together' function and Object->Optimize Vertices can be
used to remove duplicate points.
Setting the revolve offset allows the profile to be moved along an axis for each revolution. This is useful for making
spiral pipes, springs and screw threads.
Example: creating a spring:
Example: creating a thread
Mirror
The mirror function duplicates all object surfaces and vertices and flips the new surfaces and vertices around the
specified axis.
Examples:
A hemisphere
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Object->Mirror-> +X
Object->Mirror-> -X
Object->Mirror-> X axis
Where possible, Mirror will remove duplicate vertices. If mirroring half of a shape, use Vertex->Align to Axis to align
the inner edge vertices to an axis. Alternatively, select the inner vertices and resize one dimension to zero – this
flattens the selection, aligning the vertices.
Mirror is useful after use of the AC3D real-time Mirror function (View menu) where half of a symmetrical object has
been worked on.
Boolean
Boolean operations allow objects to be cut and intersected with one another. See the chapter dedicated to Booleans.
Optimize Vertices
This function removes duplicate vertices from each selected object. For vertices to be removed an object must own
the vertices and they much match the sam e position exactly. The function will share one vertex between each
connected point. This can make the object less complex and means that vertex normals can be calculated if smooth
shading is required. This function also rem oves duplicate vertex references from the surface - something that might
cause a bad polygon. If vertices do not match the same position, Vertex->Snap Together or Vertex->Snap Together
by Distance can be used to move them to the sam e point.
Optimize Surfaces
This function removes any duplicate surfaces and any polygons that consist of 1 or 2 vertices (these may exist if
vertices have been deleted from an object). AC3D highlights invalid polygons by displaying them as cyan lines.
Reduce
This function reduces the number of vertices (and polygons) whilst trying to retain as much of an object’s original
shape as possible. This is useful for saving on storage space and for speeding up the rendering of complicated
objects. This function can be used to create different objects that will be shown at different distances (LOD – level of
detail). For example, a car object should be viewed close up with all polygons, but from a distance a m ore simple
shape is adequate and can save drawing time.
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A target percentage specifies the proportion of vertices that are to remain. For example, if an object has 100 vertices
and “80%” is entered, the final object will contain 80 vertices.
The original object can remain in the model, or it can be replaced with the new object. If the original object is kept,
the new object will be created in the same position and will be selected.
An example:
732 surfaces, 376 vertices
Reduced to 40% gives:
276 surfaces, 150 vertices: a saving of 456 polygons.
The reduce window remains visible so that different reductions can be tried (use Edit->Undo to revert to the previous
state).
Subdivide + / Subdivide These functions change the subdivision level. A surface subdivision is where each surface is divided, and then the
shape of the overall object is ‘smoothed’.
Original object
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Single subdivision
Two subdivisions
Three subdivisions
without surfaces displayed:
Commit subdivision
This function affects objects that have the subdivision preview level set to a value larger than zero. The subdivision
preview level is set from Tools->Object Property Editor or by adjusting the subdivision level from Object->Subdivide
+/- (also from the toolbar controls).
It converts the subdivision preview into real polygons for the selected objects.
See the section on ‘Subdivision surfaces’ for more inform ation.
Re-centre
Object centres define the ‘local origin’ of AC3D objects. Object centres can be seen by switching on the '+' button on
the main Orth menu. This function sets this origin at the centre of gravity. This can be useful for specifying where the
pivot points or local-origin of an object are.
Minimum-centre
This function sets the object-centre (object's origin) to the minimum xyz of the object.
Fragment
Fragment creates one object per surface of the original object so that each object contains only one surface and the
necessary vertices. The surfaces are no longer 'smoothed' together - this is because each surface is now a separate
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object and vertices cannot be shared across objects. If you need to extract a number of surfaces from an object,
using Surface->Cut Away Object is recommended.
Merge
This function places all of the surfaces from the selected objects into one single object. This does not optimize the
vertices so that they can be shared across the surfaces. Use menu Object->Optimize Vertices after merging to create
a more efficient object and/or get smooth shading across adjacent surfaces.
Explode
This is similar to fragment, but each new object is moved forward in the direction the surface is facing by a specified
amount.
Extrude Along Path
This function ‘sweeps’ a profile along a specified path to create a 3D shape. The operation works on two objects: the
profile and the path. The order in which these objects are selected is important. The profile should be selected first
and the path second (usually with shift-select). An example:
Ensuring that the select mode is Object, first select the circle, then hold down the shift key and select the line. Next
select Object->Extrude Along Path:
The shapes created by this function can easily be smoothed by using AC3D’s subdivision. In the following image,
the line has been subdivided twice, smoothing the appearance. It is possible to reposition the vertices in this line to
fine-tune the desired shape. After using Extrude Along Path, the new object initially appears the same as before but
once subdivided, has the same smooth profile as the original line/path.
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Operations on surfaces
Extruding
Pressing the extrude button on the control panel (or pressing the ‘e’ key) when there are one or m ore surfaces
selected enables the function. The actual extrude is done after the selection is dragged.
Extruding is a powerful function that can be used for a number of tasks. It works by making new surfaces at the
edges of the current selection. The original selection can be removed and/or copied to the end of the new surfaces.
Selecting one or more
surfaces
and
then
selecting
the
extrude
button on the control panel
brings up the extrude
parameters.
Here the number of sections to produce is specified. The end of the new object can be capped with a copy of the
original selection. New surfaces can have their normals reversed. Removal of the original surfaces is also an option.
After setting these parameters, the bounding box is dragged in the desired direction. If the control key is held down,
movements of the mouse are constrained to either horizontal or vertical.
The extrude function is best demonstrated with some examples. This star was made by creating a 10-sided disk,
selecting alternate vertices and shrinking the selection, using the –10% toolbar button a few times.
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The magenta lines shown here represent the normals. Normals can be displayed by switching on ‘Normals’ from the
Orth and 3D menus. Displaying the normals is used here to help determine the direction in which to extrude the
object. In the extrusion, if the selection is dragged in the same direction as the norm als, the resulting shape will hide
the front of the original surfaces. This is useful if one side of a box is being extended, but in this case the original
surfaces need to be facing outside of the final shape. This means that the surfaces need to be dragged in the
opposite direction to the norm als. Here, ‘flip new surfaces’ is used so that all the new surfaces face outwards.
This is what happens when the selection is dragged up in the plan window:
If ‘remove original’ was ticked then the star that that is being dragged will be deleted:
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Here, the original surfaces have been removed to leave a star-shaped box (without a lid). If ‘cap end’ had been
unticked, then it would have been possible to see right through the star shape.
This picture shows what happens when ‘sections’ is set to 4.
To extend an existing set of surfaces, it may not be desirable to keep the existing surfaces inside the new object.
Here is a cube that has had a single ‘Surface->Divide’. Two of the surfaces are selected.
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These surfaces can be extended without keeping the original surfaces (since they will not be visible as they are
inside the shape.)
These settings are used:
To perform the extrusion, the bounding box is dragged to the left (in either the front or plan window). Holding down
the Control-key whilst dragging ensures that the new surfaces are square to the original. This gives:
When extruding lines, ensure that Remove original is ticked and Cap end is un-ticked. This ensures that no lines
remain in the new surfaces.
It is useful to switch on the display of normals when extruding to check that the resultant surfaces are facing in the
correct direction. If they are not, select the surfaces and use Surface->Flip Normal.
Flip normal
This effectively reverses the list of the vertices in each selected surface. This reverses the way that a poly 'faces'. A
polygon is defined as 'facing' if the vertices appear anti-clockwise to the viewer. If a polygon is set to be one-sided
(by pressing the '1S' button on the control panel) then it will only be viewable from one direction - the direction it is
facing. The display of normals can be switched on in the orth and 3D windows – this can help determine if any
surfaces are facing in undesired directions.
Change vertex order
This changes the order in which the vertices of a surface are drawn, by moving the first vertex to the end of the
vertex list. This can be used to change the position of a break in a line. It can also be used to fix a bad polygon,
which has the first three vertices in a non anti-clockwise order - causing the normal (used for lighting) to be
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incorrectly calculated. If a polygon appears all black, this function may need executing (possibly repeatedly) until it
appears correctly.
Flip Triangle Edge
Given two adjacent triangles, the joining edge is flipped:
Divide
Divide creates new surfaces by splitting each
surface to make quads (four point/four sided
surfaces)
Note that because this function splits surface edges, it affects any surfaces that are adjacent to those being divided.
This image shows a box that has had the top
surface divided. The red surfaces that are
adjacent now have five points each because
the division inserted an extra vertex.
Combine
Combine takes two or more adjacent surfaces and creates a single surface.
The selected surface must share edges for this function to complete. Select the menu item or press the ‘c’ key to
execute the function.
two surfaces selected
after combine – one surface
It is possible to combine surfaces that do not lie on the same plane. It is recommended that the vertices be flattened
in order to make them lie on the same plane.
If after combining surfaces, the new surface appears black from every angle, this means that the first three vertices of
the surface form an angle of more than 180 degrees. To prevent this, the vertex order must be changed (Surface>Change Vertex Order) so that the first three vertices of the surface form an angle less than 180 degrees.
29
Flatten
This acts on multiple surfaces and aligns the vertices so that they all lie on the same plane.
Before
After Surface->Flatten
Spike
This creates a 'spike' in place of each surface selected. The
distance that the apex of the spike will be away from the original
surface is specified.
If used with a spike distance of zero, this function is useful for
breaking a surface into triangles around a central vertex.
Indent
This function creates new surfaces around the edge of existing surfaces.
If the select mode is Surface or Vertex, the new ‘centre’ surface (or vertices of it) is selected after the operation
completes.
Bevel
Beveling a surface does the same as Indent but the new centre surface is raised. Two param eters are required; one
for the distance in from the edge, the other is the distance to move the new (inner) surface forward.
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If the select mode is Surface or Vertex, the new ‘centre’ surface is selected after the operation is complete.
Make hole
This function creates a hole in each selected surface.
This image shows 4 objects that have had holes made in
them - An ellipse (set to poly surface-type), a sphere, a
cube and a disk. Notice how the insides of the sphere
and cube are not visible through the holes- this is
because the default surfaces for these objects are singlesided and face outwards. To see the insides though the
holes, these surfaces need to be made two-sided by
pressing '2S' on the control panel.
Some concave polygons may have overlapping surfaces after making holes. Vertices may need adjustment to
prevent overlapping.
The size of the hole is specified as a percentage and can be adjusted in File->Settings.
Triangulate
This splits non-triangles (i.e. polygons with more than 3 sides) into more surfaces, each new surface being a triangle.
This operation can fail if it is given a 'bad' polygon - i.e. one that has overlapping edges or duplicate vertices.
Spline
This is useful for smoothing out a 'line' object and for rounding off polygons. New points are interpolated between
existing points.
Cut away object
This function takes all of the selected surfaces and vertices and puts them
into a new object. This can be useful for extracting parts of objects e.g.
splitting a sphere into two.
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Remove surface only
This deletes any whole surfaces selected. The vertices will rem ain.
Calculate surface area
This function calculates the total surface area of the selected surfaces. Note that the total area accounts for one side
of each surface.
Operations on Vertices
The majority of functions on the Vertex menu are available when the Surface or Vertex select mode is active and one
or more vertices are selected.
Snap Together
This sets all selected vertices to the same location. The vertices can be in separate objects or the same object. The
point that they are snapped to is the average of all selected points.
Snap Together by Distance
This function moves vertices together that lie within the specified distance. This is useful, for exam ple, to join two
halves of an object together.
This picture shows a close-up of an object where
two halves have been positioned together. Notice
that there is a visible seam along the top. This is
because the two halves are separate objects.
Once the two halves have been merged together
into a single object (Object->Merge), the vertices
need to be shared in order for this seam to
disappear.
If Object->Optimize Vertices does not remove
duplicate vertices then it means that the vertices
are in very slightly different positions. The solution
is to select the vertices along the join and Vertex>Snap Together by Distance. The Object>Optimize Vertices will remove the duplicate
vertices and allow the surface to appear smooth.
Snap to Grid
This moves each selected vertex to the nearest grid position. This may or may not be the visible grid. The snap grid
is defined by 'snap grid' in settings and may be different to the 'draw grid' (which is the visible grid).
Snap Objects by Vertices
One vertex in each of two separate objects should be selected before executing this function. The objects will be
moved together so that the two selected vertices are in the same location.
Smooth Shape
This function repositions the selected vertices in order to smooth the shape of the surfaces.
Align to Axis
This function moves all selected vertices so that they lie on the specified axis.
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Weld
Weld removes duplicate vertices where more than one vertices lie in the same position.
Unweld
This creates new vertices so that each surface will access a unique vertex in the same object. New vertices will be
created in the sam e location as the originals.
Insert Vertex
This function inserts a new vertex between each selected pair of vertices. Insert Vertex is useful for adding extra
points into a line.
If the two vertices selected are on an edge which is shared by two or more surfaces, only one vertex will be created,
but it will be shared across the surfaces.
Divide Triangle Edge
This function takes two selected vertices and divides the edge between two triangles. This splits each triangle into
two further triangles.
two vertices selected
after the edge division
Extrude Edges
This function provides a quick way of performing a simple extrude on one or more surface edges (i.e. between
vertices).
Vertices selected.
After Vertex->Extrude Edges,
the new surfaces and vertices
have been created but are not
fully visible until moved.
The
selection
is
moved
upwards, showing the new
surfaces.
Slice Surface
This function is used to cut one or more surfaces across selected vertices.
Single surface with
vertices selected
two
After
Vertex->Slice
Surface – now two
surfaces
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A row of vertices around a
cylinder is selected
After
Vertex->Slice
Surface
–
each
surface is cut into two
Create Convex Surface/Object
This function uses a technique called 'convex hull' to create a new object that surrounds the vertices that are
selected. This is very useful for joining complex objects together or for simplifying the creation of som e complex
shapes.
These two pictures show the function being used to join
a cylinder to a cube.
Note that because this function makes a new object, the
vertices are not shared with the old objects.
If the whole shape i.e the original objects plus the new
part- is required to be smooth then the objects must be
merged together (Object->Merge) and then have the
duplicate vertices rem oved (Object->Optimize Vertices)
A second example uses a number of simple objects, which are 'shrink-wrapped' by this function. In this case we are
creating the fuselage of an aircraft. The objects are ellipses and a single red box. Any AC3D objects can be used
this way, either lines or polygons.
34
To get a more accurate
outline, these shapes could
have been made by placing
background images of a
real aircraft onto the views
and building the shapes on
top of those images.
After Surface->Create Convex Surface/Object menu function has been selected:
This picture shows the
fuselage object created
from the simple shapes. It
has been dragged to the
side of the original objects,
which still remain in the
scene.
It’s important to note that
the
hull
created
is
‘convex’. This means that
if there had been any
vertices that were totally
‘inside’ the encompassing
hull, the new hull object
would not have any
vertices created at those
points.
This function will also
create
2
dimensional
convex hulls, provided all
of the selected vertices lie
on the same plane. If they
are not, a 3d object will be
created.
Create Ordered Surface
This function creates a surface using the individual vertices that are selected. The vertices should be selected in the
correct order and in an anti-clockwise direction. This function works by creating a new surface and adding vertices in
the order they were selected. If vertices are not selected in exactly the correct order, a bad surface (crossing edges
or non-planar) may be created.
Create Quad
This function is used to create a four point, four sided surface from three selected vertices.
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Before Vertex->Create Quad
After new surface created
and new vertex selected
New vertex is positioned as
desired
Create 2D Mesh
This function uses a technique called ‘Delaunay Triangulation’ to calculate triangles between a set of points. When
this function is selected a plane is specified. This treats the points as 2D so that a mesh can be laid out over the
points.
Example: here are a number of vertices
in the front window.
After Vertex->Create 2D Mesh->Front is
applied.
To make vertices specifically for this function: create a line, placing each point at the desired location and select the
line and Surface->Remove Surface Only. This removes the surface and leaves the vertices. Note that this function
works convexly.
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Boolean operations
AC3D’s powerful Boolean functions take two objects and perform a volume-based operation between them.
The functions reside in the Object->Boolean main menu. Each function requires two objects to be selected.
To select two objects: first switch to Object (or Group) selection mode; one object is selected in the normal manner,
then the second object can be selected by holding the shift key and clicking (or dragging over) another object.
In the following image a sphere has been positioned to overlap with a box. The subsequent sections illustrate the
operations that can be performed from the intersection of these shapes.
Subtract
Using Object->Boolean->Subtract, the second object is ‘subtracted’ from the first as if they were solid shapes. This
image illustrates the result of the subtraction.
Intersect
After Object->Boolean->Intersect, a new object is created from the overlapping solid volume between the two
objects.
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Union
Selecting Object->Boolean->Union creates a single object from the two objects. The overlapping portion is removed.
Order of selection is unimportant.
As the function’s result does not appear to be very different to the original objects, the result is best illustrated here in
wireframe.
Before Union operation.
After Union – any internal surfaces have been removed.
Cut away
The Object->Boolean->Cut-Away function uses the second object to cut a ‘solid’ portion from the first. This function is
similar to performing a Subtract and an Intersect at the same time.
After the cut.
The cut section is moved aside.
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Knife
Unlike the previous Boolean functions, which require that both objects are 3D and closed (e.g. no open edges as in,
for example, a tube), AC3D’s two knife operations can use a 2D or open 3D object as the primary operand. In both
functions the second object (which is used as the ‘knife’) must be a closed 3D object.
After the Knife. The appearance is the same as Cut
Away but the result is a single object.
Viewing this In wirefram e shows that the box surfaces
have been sliced and no internal surfaces are created.
Knife and Cut Away
This function is similar to Knife except the original object is split into two objects along the cut edges.
The result appears to be the same as Knife but is
actually two objects.
Here, the cut away part has been move aside. There
are no internal surfaces.
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Boolean examples
Cutting a round-ended channel in a cylindrical object
A cylindrical object and an oval
object.
The channel -cutting piece is moved
to overlap the cylinder. The cylinder
is selected by clicking and then the
oval is selected by shift and clicking.
After Object->Boolean->Subtract,
the channel has been cut.
Cutting an aileron from a wing
In this case, we want to cut a solid shape from a wing and retain the cut piece. A box is positioned over the area of
the wing that is to be cut out. The Object->Boolean->Cut-Away function is used.
Before Object->Boolean->Cut-Away.
40
This image shows the aileron moved away.
Cutting multiple windows from a fuselage
This image shows a hollow cylinder
and three oval shapes. The three
oval shapes have been merged
together to form a single object
(Object->Merge) so that they can be
used in a single Boolean operation.
The ovals are moved into the large
tube so that the objects overlap.
After Object->Boolean->Knife-andCut-Away, the pieces cut are in oval
holes.
This image shows the model after the ovals have been
moved away from the main tube object.
If Object->Boolean->Knife had been used, the window
shapes would still be part of the main object.
Note that for the knife functions, the main object (first
selected) does not need to be 3D and closed.
Cutting a solid object at an angle
41
This image shows a cylinder and a box. The box has
been positioned at an angle over the end of the
cylinder.
This shows the result of selecting Object->Boolean>Cut-Away.
A wireframe view shows the end of the cylinder fully
enclosed inside the box. Anything inside the box will be
cut away from the cylinder.
The cut piece has been moved
If Boolean->Object->Knife-Cut-Away is used,
the object has been cut but is no longer solid
42
Hints and Tips
To perform successful Boolean operations:
•
•
All objects should be three-dimensional and have no open edges: the object should appear ‘solid’. The
exception for this is the main object being used for one of the knife functions – this may be open or 2D.
The knife objects (the second selected object which is used to cut) must be 3D and closed.
All surface normals should be facing outwards. This can be checked by displaying normals (3D and Orth
menus, or pressing ‘n’ to toggle). When showing normals, the magenta lines should be facing away from
the surface. If a surface normal line is not visible or appears as a magenta dot, the surface should be
flipped with Surface->Flip-Normals.
Many triangles may be created if holes are created in a single polygon. It is often better to divide a single surface
(Surface->Divide) before performing this type of Boolean operation.
To check overlapping objects before performing a Boolean function, it sometimes helps to view the model in
wireframe – press the ‘w’ key or use the controls on the main Orth and 3D menus.
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Subdivision Surfaces
Modeling with subdivision surfaces makes it easy to create smooth objects using simple polygon objects.
In AC3D, any polygon or line object can be subdivided. This includes objects containing ordinary (poly) surfaces and
also lines and polylines. When an object is subdivided, the original geometry is used as a ‘base’ model. Any
changes to this base model are instantly reflected in the smoothed subdivision.
Changing the subdivision level
The subdivision level can be quickly changed by using
the Subdivide +/- items on the Object menu, or by using
the toolbar buttons Subdiv +/-. Any whole or partly
selected objects will have the subdivision level altered
(subject to the maximum and minimum subdivision level)
The subdivision level can also be altered by editing the object property from the Object Property Editor tool in the
Tools menu.
Changing the subdivision level is not a permanent change to the geometry. AC3D still maintains the original object
and any changes to this original object affect the subdivision.
All of the functions that work on normal surfaces are still functional. Adjusting the original surfaces directly affects the
subdivided object.
Objects retain the subdivision property when AC3D files are saved. To export the model into another file format,
keeping the smoothed subdivided shape, the objects can be transformed into full polygon objects by using Object>Commit Subdivision.
A setting in File->Settings defines a maximum number of surfaces for a subdivided object (Advanced->Subdivision
maxsurfaces). If this maximum is exceeded when the subdivision level is changed, a message is shown and the
subdivision will not proceed. The default value is chosen for average computers. For faster machines, the value can
be increased.
Switching display of subdivisions
The display of subdivisions is easily changed by pressing the ‘d’ key. It is possible to have different settings for orth
and 3d views e.g. orth views display the base (non-subdivided) model and the 3D view shows the full subdivided
model.
44
Switching off the display of subdivisions in all views can be useful when working on large/detailed models, since
AC3D will only calculate the subdivision when it is needed for display. Working without displaying subdivisions can
therefore speed up interaction with the 3D model.
The main 3D menu has an option to simultaneously display the original base object as well as the subdivisions. This
can sometimes be useful to see how the original object directly affects the subdivision.
Committing subdivisions
To apply the subdivision permanently, i.e. to create a new non-subdivided object with the same polygons as the
subdivision, use Object->Commit Subdivision.
Examples
Subdivision works by dividing each surface and then smoothing the overall shape.
An example – a simple box:
0 subdivision level
1 subdivision level
2 subdivision level
45
3 subdivision level
Note that the default surface type for a box
is flat. Setting this to ‘Smooth’ and setting
the object property for ‘Crease angle’ to
180 ensures that the object is fully
smoothed. (Display of the surfaces has
been switched off for this picture)
These images show a simple cup shape that was formed by using Object->Revolve on a line. The number of
segments was set to 6. The image on the right shows this same object with subdivision level applied.
Hints and tips
Although any polygon in AC3D can be subdivided,
subdivision works best with quads (four point/sided
surfaces) since they divide symmetrically.
A cube is a good starting point for many models since each face can be extruded and the vertices moved to form
other shapes, whilst retaining a single closed object with no holes. The block object is also a good base for building
subdivided objects.
Using Extrude to add detail
Extrude is the best way to add extra detail to a
subdivided object. These settings are recommended for
extruding 3D subdivided shapes:
46
A simple way to add stronger defined edges to a model
is to extrude with zero movement. This can be done by
switching into extrude mode and simply clicking on the
bounding box. The extrusion will be performed but no
movement takes place. In the example here the left
object is a cube with the top surface extruded. The right
object is a copy of this object but with no subdivision
level set – note that although it looks the same as a
normal cube, there are actually extra surfaces around
the edge of the top surface.
Display or hide subdivisions?
This image shows a cube with the top surface selected.
Notice how the bounding box is not located directly over
the selected surface (as it would be with a nonsubdivided object). This is normal, since the bounding
box surrounds the original (non-subdivided) geometry.
Switching off the display of subdivisions (press ‘d’)
shows why; the actual surface selected, in the original
object is in a slightly different location because the
subdivision causes the shape to change.
A similar effect can be seen in Vertex select-mode. Here,
two vertices are selected – note how the selection shows
around the area of the original vertices. This is because
it is the original vertices that are affected; the subdivision
is based on their positions.
Choosing the right subdivision level
Subdividing an object by one level increases the number of surfaces in that object by (a minimum of) four times and
each subsequent subdivision increases this number by a factor of four. Each level of subdivision increases memory
requirements and will have an effect on speed since there are many more polygons to be drawn and processed.
The number of vertices and surfaces in a
subdivided object can be view from the
Model Info tool on the Tools menu:
For general use, level 2 gives a smooth appearance to objects whilst keeping polygon counts lower. Obviously,
machines with large amounts of memory, fast processors and fast graphics accelerators can work with larger models
more easily.
Advanced users
The default maximum subdivision level in AC3D is 3. This can be increased in the advanced settings. You should
be aware that any increase in subdivision levels increases the computational requirements.
47
Texturing
Each AC3D object can have one texture. A texture is set from the Object->Texture menu.
Setting a texture
Each AC3D object can have one texture applied to
its surfaces.
After selecting an object (or objects), use the menu
Object->Texture->Load Texture to set a texture.
AC3D loads a number of different picture file
formats as textures. These include .gif, jpeg etc. To
view which formats AC3D can load, see the load
texture dialog.
Note that some export formats (or rather the programs that load the files) do not support all the texture file types that
AC3D supports. You should ensure that you are using the correct format texture for the correct export file type e.g.
.jpg or gif for VRML.
Changing the mapping
Texture coordinates determine how a texture is mapped onto the surfaces of an object. All AC3D objects have
default texture coordinates applied to them when they are created. A cube for example has mapping set so that one
instance of the texture will appear on each face.
Some external files have formats that do not contain texture coordinates and some AC3D operations may cause
these coordinates to become disturbed; in these cases it is necessary to remap the texture coordinates.
Changing the texture repeat and offsets
The texture repeat and texture offset for an object can be modified in Object->Texture->Set texture repeat/offset. The
texture repeat indicates the number of times the texture is to be fitted into that dimension.
Example: a cube with
texture repeats set to 1, 1
(the default):
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Object->Texture->settexture repeats/offsets and
repeats set to 2, 2:
The texture offset determines how far across the texture the mapping should start.
Texture repeat set to 1,1
and Texture offsets set
to 0.5,0.5:
If more than one texture is required on a single object (e.g. a different im age on each side of a cube), the object
should be split up into parts (e.g. use Surface->Cut Away Object) and a different texture mapped on to each of the
sub-objects.
Alternatively, it is more efficient to create a single texture im age (i.e. a single picture file containing all the required
images) and use AC3D’s Texture Coordinate Editor tool to map parts of the object.
49
Tools
This section describes AC3D’s integrated tools. Tools are accessed from the Tools menu. Other tools can be added
to this menu via software plugins.
Model Information
This displays information about the current model.
This shows the information for a single cube. Note that the total number of objects shown is actually two. This is
because the ‘World’ object is included in this count. The internal world object is the top-level container object. This
window can remain visible whilst other work continues, but if any changes occur to the current AC3D model, the
‘refresh’ button must be pressed in order to update the displayed information.
Render
This tool is used to start up an external renderer (such as a Raytracer like Povray) or other linked program. See the
rendering section for more information on how this is configured.
Object Hierarchy
This window shows the structure of the current model but also allows control over the structure of the hierarchy.
Clicking on one of the items in the list can select or unselect objects. This selection is sensitive to the current select
mode being used. In Group- select mode, for example, it is only possible to select top-level groups. To select
individual objects, switch to Object -select mode (using the main AC3D control panel).
The eye icon shows/controls visibility (similar to Hide/Unhide on the main AC3D control panel). The padlock icon
controls/shows if an object is locked.
A right click on an object item will reveal a popup menu:
50
This allows control over hiding, a more detailed properties viewer, editing object data and the option of moving an
object to the head (start) or tail (end) of the children list.
Object Property Editor
Objects have properties that can be adjusted using the Object Property Editor. The crease angle and subdivision
level can be adjusted by moving a slider and pressing a set button. Every AC3D object can have a URL (web link
address) and text data attached to it. This is a string of text. This data is saved in the AC3D file, along with the
object geometry inform ation.
Objects exported in VRML files will have a link generated around them if a URL is present, and Povray objects can
include object data text at the end of each object description (allowing custom Povray commands to be added).
The Loc point defines the position of the centre of the object. This is the local origin of the object.
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Texture Coordinate Editor
AC3D’s integrated Texture Coordinate Editor (TCE) allows full control over the texture coordinates that are applied to
all surfaces in AC3D objects.
To start the TCE select: Tools->Texture Coordinate Editor.
To edit the texture coordinates of an object, select a single object, or surfaces from a single object (in the main AC3D
windows). The TCE runs in conjunction with the main AC3D program so it is possible to switch between the
windows, selecting the surfaces and objects you wish to edit. Note that if a group object is selected (which has
textured children) then nothing will appear in the TCE. In this case, switch to Object –select mode and select a single
object.
The surfaces selected in AC3D will appear in the TCE according to their texture coordinates. All AC3D primitive
objects (those created from the control panel) have default texture coordinates. For example:
Mesh
Disk
Cylinder
Sphere
It’s important to realize that the pictures here represent the coordinates that are attached to each vertex reference in
each surface and have no relation to the layout of the actual object vertices.
52
Note that the pictures above show the texture mapping for objects that have no textures applied. If there is a texture,
it will be shown in the window.
Selecting and manipulating
When surfaces are selected in AC3D and the TCE is visible, the texture coordinates of those surfaces are all
visualized. The TCE allows editing of all, or a subset of, the texture coordinates.
The TCE has two modes of selection: Surface and Vertex. In Surface-select mode, the texture coordinates are
selected, moved and size by manipulating individual surfaces. Vertex- select mode allows individual texture
coordinates to be manipulated.
Surface select mode
Vertex select mode
Manipulation in the TCE is similar to the main AC3D 2D views. After a selection is made, the green bounding box
can be moved; the handles can be dragged to resize the selection and the selection can be extended and negated
(shift left mouse, shift right mouse). The selection can also be rotated using the mouse. When the mouse pointer is
over the edge of the bounding box, the pointer changes to indicate that if the left mouse button is dragged the
selection will be rotated.
Resizing
Moving
Rotating
The Flip buttons mirror the selection either vertically or horizontally.
Flipped vertically
Flipped horizontally
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Remapping the selection
The ‘Front’, ‘Side’, ‘Top’ buttons ‘project’ the texture onto the surfaces in the specified
axis. The bounding size of the selected surfaces determines the boundaries of the
mapping. The ‘spherical’ button causes the texture coordinates to be ‘wrapped’ around
selected surfaces.
It is possible that after starting the TCE and
selecting an object the window appears blank. It is
likely that the object has zero value texture
coordinates e.g. each surface-vertex reference has
0.0, 0.0 as a coordinate. In a case like this, a
‘Select all’ in the TCE would reveal that all of the
coordinates are set to 0, 0.
In this case, you will need to make sensible
coordinates for your model, probably in groups. Do
this by selecting a number of surfaces (from within
AC3D) and using the remap buttons to assign a
mapping to the texture coordinates. You can then
reposition and size the surfaces in the TCE and
map them onto a texture.
Replicator
The Replicator allows multiple copies of the selection
to be created. Each copy can be moved, rotated and
scaled. The Replicator also allows objects to be
extruded.
The replicator works by first duplicating (or extruding) the current selection. It then m oves the new copy using the
distances specified by Translation (X, Y, Z coordinates). If there is a rotation specified it rotates the object around the
specified location. Finally if the scale fields are set to anything other than 1,1,1, the copy is scaled.
Examples:
Creating an array of 5 objects, 1 unit apart (in the X
dimension)
54
Creating four copies, scaling each time:
Extruding a ‘horn’ shape from a single ellipse.
Creating a single step for a spiral staircase by extruding
a rectangle
Use the replicator to duplicate the steps in a spiral
pattern.
55
Create Text
The Create Text tool, which is to be found in the Tools
menu, generates 2D and 3D objects from TrueType
fonts.
This image shows the same text in Outline, Solid,
Extruded and Beveled type.
The font size specifies the maximum unit height of the text. The font detail (1 to 10) controls the number of vertices
per letter. The greater the detail, the more surfaces and vertices will be in the resultant AC3D objects.
Align Objects
This allows objects to be repositioned relative to one object. Select a single object and then shift-select others. On
pressing ‘Align’, the first object is used as the reference object.
Position 3D cursor
The 3d cursor specifies a position in 3D space. It is useful when creating
objects since it specifies the ‘missing’ axis. For example, when a sphere is
being drawn in the front window, the mouse movements specify the X and
Y position of the sphere; the Z position comes from the location of the 3D
cursor.
The default position of the 3D cursor is at the origin 0, 0, 0.
Many users find that they never need to adjust this, but it can be useful to change its position, when working on large
models away from the origin.
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Materials
The palette
The scrolling window of buttons near the bottom of the control panel represents the palette of colors/materials
available. The default color for an object is palette entry 1 (usually white).
The colored buttons are pressed to change the material on the currently selected objects/surfaces. Setting the
material of surfaces works in all selection modes, but for a surface to change color in Vertex mode it must have all
vertices selected. Note that the color on the palette button represents the diffuse color for that material.
New palette buttons are appended to the list when a file containing extra materials is loaded.
When surfaces have a texture as well as a material, that material can affect the way the texture appears. To make a
texture appear as the original colored image the surface color should be white.
To find the material index of an existing polygon, select that surface and the message at the bottom of the AC3D
window will display the material number.
Editing Palette entries
Pressing the right mouse button on a palette button
pops up a menu. The options are to edit a color, select
all surfaces with that material or add a new material. A
copy of the selected material will be added to the end
of the list.
Pressing the colored button brings up a system color
selection.
Pressing the ‘+’ button next to an item expands the
item so that the numeric values of the Red, Green and
Blue components can be altered with sliders.
The material window allows various attributes of the material to be altered
Diffuse
This is essentially the main color of the material. The exact shade shown on a model depends on
the amount of light available to the surface
Ambient
Ambient color works with the diffuse to affect the overall color of a surface, but is not sensitive to the
amount of light on that surface.
Emissive
Setting this can make a surface appear to be giving off light. This may be used, for example, to give
a light blue glow to a spaceship’s engine. (No actual light is emitted from surfaces with an emissive
color set.)
Specular
The specular quality defines the color and brightness of highlights. This works in conjunction with
Shininess.
Shininess
Transparency
A high value means that highlights will be smaller and less scattered across the surfaces.
Transparency can be useful to for making a surface look like glass. Transparency is supported in the
palette but for purposes of speed the surfaces are not sorted when they are rendered into the views.
If the ‘real-time update’ option is selected, any 3D view windows are redrawn every time a change is made to the
material.
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Loading and saving files
An AC3D file (usually named <som ething>.ac) is a text file describing the geometry of a model. AC3D files retain all
available information about a model built with AC3D e.g. textures, surface settings, materials, object data etc. Other
file formats exported by AC3D may not retain all of this information. Models should always be saved in this format to
ensure that no detail is lost.
Developers can view a description of the file format on the AC3D website.
AC3D files are loaded by selecting File->Open. This will replace the current model. To load models in addition to the
current model, use File->Merge.
A list of the most recently opened files appears on the File menu. Selecting one of these causes it to be loaded.
Importing other formats
See the File->Import menu for a list of file types that AC3D can import.
Extra Import/Export plugins allow AC3D to handle more file formats. Check the AC3D website for details of additional
plugins.
The following formats may be useful for importing your own model data.
Triangle files
The format of triangle files is: each line contains 9 floating point numbers and one hex value e.g.: 0.0 0.0 0.0 1.0 0.0
0.0 1.0 1.0 0.0 0xffffff represents 3 vertices of a triangle. Hex value is 0xRRGGBB col - in this case white duplicate
vertices are aggregated when loaded.
Vector files
This is another simple format for importing 2D vector data. Each line should consist of a number of vertices followed
by the same number x/y coordinate pairs e.g.
3 0.5 0.5 2.5 2.5 10 5
This represents a line with 3 vertices (0.5, 0.5) (2.5, 2.5) (10, 5)
Exporting files
AC3D can generate output files for many different formats. Support for extra file formats can be added by installing
additional AC3D plugins. See File->Export for a list of the output files supported. Several are mentioned here.
3D Studio (3ds)
3D studio files are used in 3D Studio Max 3D software. This is a long established binary format which is supported by
a lot of third party software. Note that objects with > 1 material will be split into separate meshes within the 3DS file.
VRML 1
VRML is an ASCII geometry file specification used for web graphics. VRML files may be viewed from within any web
browser that has an appropriate plugin installed e.g. Cortona
http://www.parallelgraphics.com/products/cortona/.
AC3D Object URLs (set from the object data dialog) are used so that objects will be selectable in the appropriate
browser. The output of normals and textures can be switched on/off in the File->Settings window.
VRML 2
VRML 2 is a geometry description web file format which also allows animation and some other powerful constructs.
See VRML 1 for a suitable browser plugin.
Output of normals and textures is switchable via Settings.
VRML2 Proto
This form of VRML2 output exports objects into a VRML prototype. This can be used when compositing larger
models where each object may be stored in an individual file and a single file controls the locations of individual
instances.
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DIVE
Dive is a Virtual Reality system. The Dive generation will include the object data (if you have input any); this is
usually TCL code. If an object has a URL then the object will be a dive gateway. See http://www.sics.se/dive for more
info about the Dive VR system.
MASSIVE
Massive is a distributed VR tele-conferencing system written by Chris Greenhalgh at Nottingham University in the
UK. It runs on SGI and Sun platforms. For more details, see:
http://www.crg.cs.nott.ac.uk/~csm/massive.html
RENDERMAN
These files are used in a raytracer. This allows detailed images with accurate lighting, shadows and reflections to be
created from a 3D model. There are a number of Renderman- compatible renderers available. The eye viewpoint is
defined by your view position in the primary 3D window (approx). Note that lines will not be output. Any polygons that
need triangulating (breaking up into triangles) will be triangulated.
POV-Ray
POV-Ray is a very popular raytracer; see www.povray.org for more inform ation. The eye viewpoint is defined by the
view position in the 3D window. In Spin mode the viewpoint will be approximate; for a more accurate viewpoint
position switch to walk-mode in the 3D window.
The color palette is output at the top of the file; each entry has the same number as the AC3D material. The
properties can be altered easily to provide different surface types and textures (some #includes can be added at the
top of the file to get external definitions). The light is output at the end of the file. The light’s position is the same as
the viewers. The POV-Ray output is based on triangles; lines will be ignored and polygons with more than three
vertices will be triangulated automatically.
The Object data text, specified in Tools->Object Property Editor, can be used to attach information to objects which is
then inserted into the POV-Ray file. ‘Use object data in POV files’ in the main AC3D File->Settings must be ticked
so that this text is inserted into the file. A POV-Ray include command may be inserted in to the setting ‘POV header’
e.g. #include "glass.inc".
See the Rendering section for an example of using POV-Ray.
Triangle files
See loading triangle files for a description of this format. This format is very simple and is easy to parse.
Object Library
The object library is accessed from the File menu and
can help organize and maintain a structured set of
model component objects.
Objects may be added and removed from the library. For
example, these ‘components’ may be electronic parts,
kitchen units, molecule models etc.
Loading a single object from the library can be repeated
to make multiple copies of the same object.
Note that the 3D position at which the object is saved
will be its location when it is loaded again from the
library.
To add an object to a library, select it and press “Store”.
Take care when replacing objects, as the object that is
currently selected in AC3D will overwrite the file stored
on the library.
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Rendering
The "Render" tool in the tools menu can be configured to automatically launch an external renderer. This allows
generation of high-resolution images with shadows, reflections, transparency and other effects.
The output file type is set from the ‘Output file type’ pull-down menu. The file types listed here are all of the file-types
that AC3D can export (extra file-types may have been added using plugins).
The ‘Output filename’ specifies the name of a file that the model will be generated into.
The ‘Render program’ specifies the program that will start after the file is written.
The ‘Render Param eters’ are appended to the command line that it executed to start the render program. If a ‘%s’ is
specified in the render command, it will be replaced by the render filename.
A POV-Ray example
POV-Ray is a very popular ray-tracer - see www povray.org.
This example shows a very simple model
consisting of a mesh, a sphere and a cube
that has been divided a couple of times (with
Surface->Divide), then had a Surface->Make
Hole operation. There is also an extra light
present in the model.
The sphere has had a pov texture specified using the Tools->Object Property Editor (the appearance of the object in
AC3D will be unaffected by this):
The settings in File->Settings were:
Pressing the Render button in the Render Tool gives:
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The Povray exporter supports bitmap-textured objects. Ensure that the formats of the texture picture files used are
compatible with POV-Ray.
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Appendix
3D Mouse support
AC3D supports 3Dconnexion’s 3D navigation hardware. There are a number
of different motion controllers available from 3Dconnexion, all are compatible
with AC3D. A 3D mouse can be used in the AC3D’s orthographic (2D) views
and in 3D views (in both spin and walk modes).
In AC3D’s Orth/2D views, a 3D mouse will pan (move left/right/up/down) and
zoom. In a 3D view in spin-mode, the 3D mouse will act as if the selection is
being handled (this is commonly called object-navigation in many CAD
applications). In a 3D view in walk-mode, the 3D mouse is used to walk/fly
around the scene as if the camera is being controlled (commonly called
camera-m ode navigation).
AC3D can be configured for both user preferences for zooming. Zooming can
be performed either when the 3D mouse is pulled up/down or when it is pushed
forwards/backwards. The following im age shows a configuration dialog from a SpaceNavigator. In AC3D, this is
shown when the right button on the SpaceNavigator device is clicked.
In this image, zooming is set for up/down on the SpaceNavigator.
There are two 3D mouse related settings in AC3D which can be altered. See menu File->Settings->Advanced:
These settings affect the way the SpaceNavigator controls rotation.
For up/down zoom direction, the rotating is done when the 3D mouse is twisted left/right. For forward/backward
zooming, the rotation is controlled by tilting the 3D mouse left and right.
If zooming is set to up/down, as in the SpaceNavigator dialog image above (green arrows), these two settings should
be left un-ticked. If the 3D mouse zoom is set for forward/backward (blue arrows), tick these settings.
The left device button on the space mouse is set to ‘Fit’. This moves the display focus to the center of the current
selection. An example; if you are navigating in spin-mode and wish to work on another object or part of an object,
62
change the selection and press the fit button. The right device button is set to bring up the settings dialog. Pressing
this button again dismisses the dialog.
For more information on 3Dconnexion’s devices, see www.3dconnexion.com.
Plugins
Plugins add extra functionality and additional file format support to AC3D. Plugins files are usually named
<something>.p and reside in the Plugins folder within the AC3D installation. Additional tcl files in the same folder
may also provide user-interfaces and scripting for use with some plugins.
Plugins are automatically loaded when AC3D starts. The console displays the progress of loading plugins and will
show any errors that occur. It is important that plugins are designed to run with the correct version of AC3D, or they
may fail to load.
To find out more about the plugins that are currently installed, use Help>About Plugins.
Selecting each plugin line brings up a description and any associated
instructions for the plugin.
Performance tips
Rendering more polygons takes more time. As larger and more detailed objects are edited, the rendering will take
longer. Here are some tips to help edit larger models more effectively.
•
•
•
•
•
•
•
•
Switch to wirefram e viewing. This is faster to render than filled graphics.
Use object hiding and locking. This reduces the graphics load.
Edit in only one maximized view. This prevents all views from being updated every time a change is made.
If surfaces can only be viewed from one side (e.g. they are outer surfaces of a closed object such as a
box), set them to single-sided. This is slightly faster to draw.
Switch on ‘interactive-wireframe’ in both the Orth and 3d menus. This temporarily sets the view to
wireframe when being panned or zoomed using the mouse. Wireframe usually renders faster than filled
polygons.
The ‘Interactive Wireframe’ switches, located on the main Orth and 3D menus, will switch the views into
wireframe for manipulations.
When using surface-subdivision keep the subdivision preview level set to 1 or 2 when working on the
object. Switching off the display of subdivisions will also speed up interaction.
Use Object->Reduce to reduce the number of vertices/polygons in an object.
Key-presses
Key shortcuts for menu items are shown on the menus. Other keys can be used:
In orthographic (2D) windows:
Key
Function
Cursor-keys
move view
Shift-Cursor
move view faster
Control-up
zoom in
Control-down
zoom out
Shift-Control-up
zoom in with larger step
Shift-Control-down
zoom out with larger step
Alt-Cursor
move background image
Alt-shift-cursor up/down
scale background image
Backspace/Delete
delete current selection
Space
maximize or minimize the current view
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t
toggle textures
o
set select mode to OBJECT
v
set select mode to VERTEX
s
set select mode to SURFACE
m
set drag mode to MOVE
r
Set drag mode to ROTATE
e
set drag mode to EXTRUDE
f
fit selection to window
control-f
fit selection to all views
g
toggle grid
h
hide selected objects
z
zoom in
x
zoom out
Space
maximize/minimize view
Some of the keys for the 3D window have an equivalent menu item in the 3D menu.
In 3D views:
Key
Function
w
wireframe/filled toggle
t
toggle textures
g
toggle 3d grid
f
fit to window/centre spin view around the selection
Space
maximize/minimize view
In the 3D window, the cursor-keys spin the model in 'spin-mode'. In Walk mode, they control the viewpoint in a
similar way to 'Quake' and other games e.g. left, right, forward, back, alt-up/down move up/down, control-up/down tilt.
Preferences/settings
The settings in File->settings are saved automatically when you exit AC3D. This automatic saving can be switched
off from the settings window. Settings must be saved with this set to ‘off’ for the change to be remembered.
Under Mac/Unix, the settings are saved to $HOME/.ac3dprefs. Under Windows, they are saved to the user’s home
directory as ac3dprefs.txt.
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Additional Information
Third-party plugins
There are a number of additional plugins that add extra functionality to AC3D. Some are supplied with AC3D and are
described here, others are available via the AC3D forum pages – see the website for more information
Greeble
From SuperColdMilk, this excellent AC3D plugin makes it easy to add detail to your models.
Greeble is an AC3D plugin that adds greebles to existing geometry. Wikipedia defines a greeble thus: “…a small
piece of detailing added to break up the surface of an object to add visual interest to a surface or object, particularly
in movie special effects."
Greebles are placed in a separate object from the base object. Your base geom etry is not modified.
The Greeble user-interface is accessible from the AC3D Tools menu.
There are many options, the parameters are described here.
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Parameter
Usage
Beveling
If checked, bevels will be placed on selected surfaces prior to adding
greebles. This is often used to get a discontinuous "raised floor" effect.
Bevel frequency %
The frequency with which bevels are applied to surfaces. For instance, a value
of 75% means roughly 3/4 of the selected surfaces will be beveled.
Bevel minimum height %
Bevel maximum height %
The minimum/maximum height that a bevel will be raised on a given surface
(the actual value per surface is random). Beveling uses a formula that takes
the area of the underlying surface into account. This number may exceed
100%.
Bevel minimum indent %
Bevel maximum indent %
The distance from the edge of a surface that a bevel will start. Specify zero to
have bevels at the very edge of a surface.
Bevel division frequency %
The frequency with which bevels will be split into 2, 3, or 4 separate bevels. If
a bevel is split, the split between 2, 3, or 4 bevels is random. This feature only
works on quads, not triangles.
Greebling
If checked, greebles will be placed either on the tops of bevels, or directly on
the tops of surfaces where no bevels exist.
Greeble frequency %
The frequency with which greebles are applied to surfaces. For instance, a
value of 75% means roughly 3/4 of the selected surfaces will be greebled.
Minimum greebles per surface
Maximum greebles per surface
The number of greebles that will be applied to each surface.
Greeble minimum height %
Greeble maximum height %
The raised height of each greeble. Greeble heights default to the surface area
of the underlying surface. This number may exceed 100%.
Greeble minimum size %
Greeble maximum size %
The size of each greeble as it is spread on the surface. 100% means the
greeble will completely cover the surface.
Greeble rotation degrees
Greebles are randomly rotated when placed; this value dictates the increment
(in degrees) which a greeble may be rotated, from 0 to 90.
Random seed
A seed for the randomizer used to determine greeble placement. Use a
number here for consistent results between greeble runs on the same objects,
or specify one (1) for a number based on the current date/time.
Use custom greebles
If checked, custom greebles will be located and used (if present). See the
"Custom greebles" section below.
Use standard greebles with custom If custom greebles are found and this box is checked, the custom greebles will
be combined with standard greebles. If this box is not checked, standard
greebles will not be used unless there were no custom greebles found.
Maintain custom greeble aspect
If checked, custom greebles will not be distorted to conform to the underlying
surface. Use this for greebles where you wish to maintain their current
width/depth/height aspect ratios.
Note that this works best when placing greebles on relatively
square/rectangular objects. When placing un-distorted greebles on triangles or
skewed polygons, they may tend to gravitate toward the weighted center of
the polygon rather than.
Greebles in separate objects
If checked, each greeble/bevel will be created in its own separate object. All
greebles are then grouped into a single AC3D group.
Note that this can cause significant slowdowns if you end up with thousands of
greebles/bevels in separate objects.
Realtime updates
This feature provides you with an interactive preview, directly on your selected
surfaces, of what your generated greeble will look like. The greebles will be
updated as you tweak/change variables.
While realtime preview is active, you will not be able to interact with your
model. You may go in and out of realtime preview to rotate/scroll your model
view to get a different perspective on the greeble-in-progress.
Note that if you manually type values in fields, the realtime preview does not
update - only when you use the numeric scrolls or the checkboxes does the
preview update.
Once you click the "Create greebles" button, the actual greebles are
generated, and realtime preview is disabled.
Save settings to greeble Data
Enable this feature to write a summary of greeble settings to the newly
created greeble object. Handy for seeing how you initially generated a greeble
object. Use the AC3D object property window to see the contents of the Data
field.
Each textual setting is prefixed by "//", which should make this POV-Ray-safe.
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Standard greebles
By default, there are 4 types of greebles, shown here.
These greebles are stretched, rotated and scaled in
accordance with the underlying surface.
Custom greebles
Use custom greebles where the standard set does not meet your needs.
Custom greebles are merely AC3D objects. To make an object a custom greeble, edit the object's Data property (F9
in Object mode) and type "//CUSTOM_GREEBLE" (without the quotes) at the beginning of any line in the text box.
Make sure you type in all-caps as shown, and do not enter any spaces.
(NOTE: A future release may make this a friendlier process).
You may define as many custom greebles as you like. If you have a set that you like to use, you could save them to
their own file and load that file into whichever document you'd like to use them.
Also, greebles should point "up" along the Y axis. Basically, the view of your greeble in the "top" view is the way the
greeble will be applied to the target surfaces.
Once you have your custom greebles created, make sure the "Use custom greebles" checkbox is checked.
Below is an example using custom greebles. The cylinder and half-sphere have been defined as custom greebles. I
have created a greebled cube with a mixture of custom and standard greebles.
Notice that the size of the custom greebles does not matter. It is copied and resized to a square area and then
proportionally placed on the target object, so it doesn't keep any proportions you initially apply.
Texture coordinates are preserved on custom greebles, but the material used will be the same as the underlying
surface onto which it is applied. Textures themselves are not applied to greebles by default (you must do that
yourself).
For more information on the Greeble and other excellent AC3D plugins, see www.supercoldmilk.com.
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© 2008 Inivis Limited
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electronic or mechanical, including photocopying, recording or storing in a retrieval system, or translated into any
language in any form without the prior written permission of Inivis Ltd.
Software license
The software described in this document is furnished under a License Agreem ent, which is included with the product.
This agreement specifies the permitted and prohibited uses of the product.
Licenses and trademarks
Inivis ltd., the Inivis logo, AC3D and the AC3D logo are trademarks of Inivis ltd. All other product names and any
registered and unregistered trademarks mentioned in this manual are used for identification purposes only and
remain the exclusive property of their respective owners.
Inivis
www.inivis.com
th
Last updated 4 July 2008
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